The New Solid-state Limiting Its Optimized Design

With the development of power system and modernization industry, the short circuit capacity of power system increases again. The situation is harder in the areas with heavy load, for the dense electrical network and complex structure, the short circuit current already reaches or surpasses the interdiction capacity of the switching gear. In order to solve this problem, people explore and research fault current limiting technology positively. In 1970s,some people proposed the concept of fault current limiter(FCL).Then many kinds of FCL appears, such as super-conductive fault current limiter, Magnetic Current Limiter, positive temperature coefficient fault current limiter, solid state fault current limiter and mixed fault current limiter.Along with the development of power electronic technology, the solid state fault current limiter will have a broader prospect of extension. This article deals with the study of series resonance type fault current limiter and the new type solid state fault current limiter. The series resonance type fault current limiter has the advantage of simple operating principle and topological structure etc. It may be designed with serial compensation following the condition of the electrical network. However, from the simulation, we draw the conclucion: in the process of restraining fault current after a fault occurrence in electrical network, capacitor and parallel inverter switch will stand for poor working condition. The current limiting effect of new solid state fault current limiter is ideal. The result simulation and the test of 10kV/500A/2500A machine support the idea. However, the issue of size and cost obstruct the fault current limiter in application.In the process of exploring the application method for the new solid state fault current limiter, based on the special function of coupling transformer, saturated transformer type solid state current limiter is presented. This article studies the saturated transformer type solid state fault current limiter in this foundation, proposes the method for primary parameter design. The performance of the saturated transformer type SSFCL on normal status and short-circuit current limiting mode have been simulated. The results demonstrate the feasibility of this program. The coupling transformer in the bridge type solid state fault current limiter adopting saturated transformer with special structural design, the size is great smaller than the conventional transformer with general structural design. And because of the saturated reactor can be equivalent to current limiter reactor while working on short-circuit current limiting mode, the bypass-inductance can be removed, also the volume of direct current reactor can reduce effectively. So the size and cost of the SSFCL can be decreased obviously.